feat: persist Authelia credentials to .env file

- setup-homelab.sh: Save AUTHELIA_ADMIN_* credentials to .env file
- deploy-homelab.sh: Check .env file as fallback if temp files don't exist
- .env.example: Document auto-generated Authelia admin variables

This ensures credentials survive reboots (e.g., when NVIDIA drivers are installed)
and the deploy script can find them even when run manually after reboot.

.env.example

@@ -38,16 +38,18 @@ ADMIN_EMAIL=your-email@example.com  # Used for admin user account
 # AUTHELIA SSO CONFIGURATION
 # ====================================
 # Generate these secrets with: openssl rand -hex 64
-# The deploy script will use these to configure Authelia
+# The setup script will auto-generate these if not set
 
 AUTHELIA_JWT_SECRET=generate-with-openssl-rand-hex-64
 AUTHELIA_SESSION_SECRET=generate-with-openssl-rand-hex-64
 AUTHELIA_STORAGE_ENCRYPTION_KEY=generate-with-openssl-rand-hex-64
 
-# Authelia Admin Password (OPTIONAL)
-# If not provided, deploy script will generate a random password
-# and save it to /opt/stacks/core/authelia/ADMIN_PASSWORD.txt
-# AUTHELIA_ADMIN_PASSWORD=your-secure-password-here
+# Authelia Admin Credentials
+# These will be auto-generated by setup-homelab.sh
+# DO NOT set these manually - they are generated during setup
+# AUTHELIA_ADMIN_USER=admin
+# AUTHELIA_ADMIN_EMAIL=admin@example.com
+# AUTHELIA_ADMIN_PASSWORD=auto-generated-password
 
 # SMTP for Authelia Notifications (OPTIONAL)
 # If not configured, notifications are saved to file instead